Demon

Demons, unlike Daemons, are extra-dimensional creatures that often descend from rifts within the universe to feed upon raw energy, like that of the human brain. Demons are, in a way, similar to Gods, except that Gods are N-th dimensional beings, whileas Demons are limited in which dimensions they may traverse. Demons can often ascend into more dimensions by collecting enough raw energy from either organic beings or energy beings, so as to be able to break through the wall between dimensions. Once thought of as aliens, Demons are now known to have entered this solar system through an inter-dimensional rift near Titan. They have so far been able to infiltrate Area 51 and many other Government compounds, but the Political leaders of earth have struck a deal, allowing the Demons to feed on any organisms but humans first. They are of higher dimensions than we, so we are thus unable to percieve their true forms. They can appear as anything to us, even remain entirely invisible if they wish to.